A French catamaran offers a different approach to power and propulsion

SAIL
Magazine has chosen the Lagoon 440 as their Boat of the Month. Below is a sea trial report by contributing editor Tom Dove, carried out on the Lagoon 440 with a prototype version
of the Hybrid propulsion system.

Reprinted with Permission by SAIL MagazineWritten by Tom Dove
December 2006

Even a short look back in time shows how accustomed we have become to luxury in our boats. We expect beautiful wood joinery, smooth fiberglass work, large electrical systems, sophisticated
nav gear, electric winches, effortless sail handling, spacious living areas, and galleys that rival our kitchens at home. The Lagoon 440 has all that, and as the TV ads say, “But
wait. That’s not all.”

The hidden secret of the Lagoon 440 I sailed in Miami is its propulsion system. This boat has no diesel drive train at all—it’s all electric. (Optional on the 440, and Lagoon
plans to offer this system on all its boats in the future.) Twin electric motors, one mounted in each hull, power the boat. They turn the props at 900 to 1,100 rpm at cruise, an ideal
speed for efficiency in this size range. Energy for the motors comes from a 22-kW diesel genset, mounted in a locker in the bridgedeck, which charges a massive storage bank equivalent
to twelve 8D-size batteries. (The extra weight of the batteries is compensated for by the lack of two heavy diesel engines mounted near the sterns and by the ability to mount the battery
weight closer to the center of the boat.) The batteries are wired in series to give 144 volts. It’s a bit like the system in a hybrid car, where the genset starts automatically
when the batteries need recharging. This happens at 50 percent to 80 percent discharge and is adjustable.

In practice, I found the electric drive nearly silent, with only a whir from the props when we ran at cruise speed. The big surprise came when the genset started. The sound level was
still so low that my decibel meter couldn’t register it, even when I held it next to the generator box. This system is literally as quiet as an air-conditioner. That’s one
of the advantages of this unique drive system. The genset can be mounted anywhere and be insulated effectively for sound. Also, the motors are quite small, generate little heat, and do
not require cooling water or an exhaust, so the designer has lots of freedom in placing them
in the hull and gains space for other uses.

But wait. That’s not all. Any electric motor works as a generator if you apply torque to turn the shaft instead of putting current into the motor and taking shaft torque out to
do work. In a hybrid car, coasting downhill puts the motor into generator mode, recharging the batteries until the car stops. In the Lagoon, sailing in a good breeze makes the props turn
the drive shaft as they move through the water, cranking the motors and generating electric current from them. That recharges the battery bank.

I’ve been skeptical of this regenerative aspect of the system because it requires substantial power from the props, but the skipper of our test boat assured me that it really works,
at least on open-ocean passages. During one trip so much current was generated in the trades that the control system shut off the motors and stopped the props to prevent overcharging
the batteries. This is splendid news for voyagers, who could have an inexhaustible source of energy for onboard systems as long as they sail. There’s a separate battery bank for
the house, along with an inverter to change the DC into AC for appliances that require it. The same genset, or the props in regenerative mode, power both propulsion and house systems.

With all this electrical wizardry, it’s almost possible to overlook the boat itself. That would be a mistake. The Lagoon 440 is a well-made vessel with lovely, luxurious accommodations.
I especially liked the space on the flybridge and the muted decor of the cabins. Tall sailors will welcome the substantial overhead clearances belowdecks. The panoramic view through the
saloon windows is not only appealing, it’s practical in inclement weather as you can sail the boat via autopilot from the comfort of this living space. For entertaining a crowd,
the saloon table converts from small to large easily. The three-cabin Owner’s version dedicates almost the entire starboard hull to a master suite. That’s a lot of room on
a vessel this size, and it includes a couple of comfy chairs, a large head compartment, and plenty of hanging-locker space.

This boat’s mission is long-range cruising by a family, or charter service, and that’s generally going to be in breezier conditions than I encountered in Miami, which limited
my test sail. Any vessel this size is out of place when sailing in light breezes and tacking in close quarters, but in the Caribbean trade winds, the Lagoon 440 will be perfectly at home.
The big cat handles nicely under either power or sail but without much feedback or helm feel. The sight lines from the flybridge are excellent. The high-cut jib minimizes the blind spot.
I found the Lagoon 440 cruised easily at about 8 knots under power and was highly maneuverable.

Sail handling on a vessel this size is a major concern, and the Lagoon accomplishes it gracefully with the aid of electric winches and conveniently led halyards and sheets. There’s
no shortage of power, thanks to the diesel-electric regenerative system. The boom is too high for me, an average-height sailor, to reach easily for flaking, but the roller-furling headsail
is easy to manage.

Conclusion
A quiet, efficient energy system in a well-made boat with all the amenities for comfortable living is an attractive package. If the Lagoon’s propulsion system proves to work in
all conditions and after years of use, we’ll all look back on the 440 as one of the first production boats to embrace the new technology. Kudos to Lagoon for pushing the envelope
by combining technical expertise, sailing experience, and aesthetics in what just could be a look into the future.

SpecificationsPrice: $500,404 for the three-cabin, three-head Owner’s version includes standard diesel engines (electric propulsion system optional), sails, and delivery (but
not rigging, launching, or taxes) to East Coast USA. Builder: Lagoon America, Annapolis, MDDesigner: Marc Van Peteghem & Vincent Prevost Construction: Hulls and decks are hand laid and then vacuum-bagged to ensure light weight and complete resin infusion. Hulls are solid fiberglass below the waterline.
Closed-cell foam core is used above the waterline to minimize weight and provide extra stiffness. The deck is cored with balsa, and areas where deck hardware attaches are reinforced with
solid glass. Rig is aluminum. Pros: Nearly silent under power, better weight distribution, better fuel economy. Cons: Only one power source (for electricity and propulsion) instead of the redundancy two separate engines provide.